The field of the invention is laminated electromagnetic actuators for electrical equipment, and particularly, laminated contactor and relay cores which can be internally lubricated or secured together.
A typical application of the laminated, metallic contactor cores of this invention is in a motor starter which preferably has two U-shaped cores around which coils of an electromagnet are wound. One core remains stationary and is referred to as a yoke, while the other is moveable and is called an armature. The two laminated cores are attracted to each other when electric power is applied to the coils so that the ends of their legs strike each other. The surfaces at the ends of these legs are preferably ground smooth to reduce vibration of the cores in the closed state. Repeated activation of the starter causes the laminations to shift slightly and also wears the surfaces of contact between the two cores. The wearing of the surfaces exposes bare metal which oxidizes, creating a rough surface ultimately producing vibration and a humming of the starter. To avoid this problem, it is customary to dip the cores in an oil for an extended period of time so that the oil will wick between the laminations. During operation of the device, the oil will seep or wick out of the laminations, coating the contact surfaces and preventing oxidation. A problem arises during manufacture of the cores that are impregnated with oil in that the oil on the outside of the coil during subsequent processing will pick up dust and other contaminants. Also, the amount of oil in the core which is difficult to inspect or accurately control affects the operation of the device.
A prior technique for fastening the laminations together placed metal plates on each side of the outer steel laminations. The assembly is clamped together and riveted. The rivets do not totally fill the holes through the laminations, allowing movement of the laminations which results from the force of repeated operations such as in a motor starter relay.
The prior art recognizes the value of providing the meeting surfaces of the electromagnet with a fine oil film. This is seen in U.S. Pat. No. 3,538,601 which provides a groove formed in conjunction with laminations to hold oil in position an oil film on the ends of the laminations that comes from the reserve between the laminations. In U.S. Pat. Nos. 4,882,834 and 4,948,656 a method and a laminate are disclosed wherein a thin layer of oil is applied by pressure to the laminations.
Concerning the connection of core laminations together, U.S. Pat. No. 3,304,358 shows core laminations and an epoxy resin placed in a passageway in order to hold the laminations together. Wicking action of the epoxy resin between the laminations is also stated.
The prior art does not provide the use of a blind hole in conjunction with the laminations for filling with a oil so as to afford a wicking of the oil from between the laminations and the outer surfaces. Neither does the prior art show the use of a blind hole for the placement of an epoxy adhesive between the laminations or the placement of an epoxy adhesive through a passage in the laminations and in conjunction with end layers for fastening the laminations together.